Carbon blacks are generally produced in a furnace-type reactor by pyrolyzing a hydrocarbon feedstock with hot combustion gases to produce combustion products containing particulate carbon black.
Carbon blacks may be utilized as pigments, fillers, reinforcing agents and for a variety of other applications. For example, carbon blacks are widely utilized as fillers and reinforcing pigments in the compounding and preparation of rubber compositions.
Carbon blacks for rubber use have a variety of grades depending upon their properties and are generally classified on the basis of analytical properties including: specific surface area (iodine adsorption (I.sub.2 No.); nitrogen surface area (N.sub.2 SA, etc.), structure (DBP absorption) and the like. Methods of measuring the surface area of carbon black include an electron microscope, nitrogen surface area (N.sub.2 SA) according to the BET method, CTAB surface area according to the adsorption of cetyltrimethylammonium bromide as a surfactant, and iodine adsorption number (I.sub.2 No.). The structure of a carbon black refers to the linkage of carbon black particles due to agglomeration. As the degree of agglomeration becomes greater, the value of this structure becomes higher.
The properties of the grade of carbon black become an important factor in determining various performances of the rubber composition wherein the carbon blacks are incorporated. Carbon blacks are effective in the preparation of rubber vulcanizates intended for usage in preparing tires. It is generally desirable in the production of tires to utilize carbon blacks which produce tires with high levels of abrasion resistance, heterogeneous abrasion resistance and grip performance properties. These properties are especially important in racing tires.
The relationship between heterogeneous abrasion resistance and carbon black properties is not well understood. However, generally, in order to impart high abrasion resistance a carbon black having both a high surface area and a high degree of structure is incorporated into the rubber composition used to form the tire. Generally a high N.sub.2 SA carbon black is also useful for improving the grip performance properties of tires into which the carbon black is incorporated.
However, a carbon black having a high specific surface area is generally believed to impart a high viscosity during the mixing step in the formation of a rubber compound. This high viscosity causes the dispersion of the carbon black into the rubber compound to deteriorate, and may thereby adversely affect abrasion resistance and heterogeneous abrasion resistance of the rubber compound. Thus, when carbon blacks having a high surface area are added during the process of forming rubber compositions the high surface area carbon blacks make the rubber composition more difficult to mix. The high surface area carbon blacks are also more difficult to disperse in rubber compositions. Further, when carbon blacks having a high degree of structure are incorporated into rubber compositions, the hardness of the rubber composition becomes unsuitable.
It would be desirable to develop a carbon black which would impart improved abrasion resistance, heterogeneous abrasion resistance and grip performance properties to rubber compositions containing the carbon black. Tires prepared with such a carbon black would be especially advantageous for use as racing tires.
Accordingly, one object of the present invention is the production of new carbon blacks which impart improved abrasion resistance, heterogeneous abrasion resistance and grip performance properties to natural rubbers, synthetic rubbers and blends of natural and synthetic rubbers incorporating the carbon blacks.
Another object of the present invention is new rubber compositions, advantageous for use in producing tires, particularly racing tires, incorporating the new carbon blacks.
Other objects of the present invention will become apparent from the following description and the claims.